1. Field of the Invention
The present invention relates to an air conditioning apparatus, wherein a flexible film member having an opening for a passage of an air flow is moved in a casing for switching the direction of the air flow in the casing.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 5-310029 discloses an air conditioning apparatus which includes a flexible film member or film door having an opening for a passage of an air flow. The film member has a first and a second end connected to a driving and a driven shaft, respectively, which are rotatably supported in the casing. The casing defines therein a passageway for the air flow. The film member is arranged so that it is located opposite to air discharge outlets which are formed at the downstream end of the air passageway. Furthermore, a driving means is connected to the driving shaft for rotating the drive shaft, which causes the film door to be moved between a mode where an outlet is opened and a mode where another outlet is opened. As a result, a desired switching from mode to mode become possible.
A test was done by the inventors of this application as to the air conditioning apparatus including a film door moved for switching a direction of an air flow in a casing. According to this test, it was firstly found that, when the flexural rigidity of the film door is too small, i.e., the film door is too flexible, an air flow pressure applied to the film door causes the latter to be wrinkled. Such an occurrence in the wrinkle causes a gap or gaps to be created between the film door and the casing, thereby allowing the air flow to leak via the gap or gaps. Thus, the flexural rigidity of the film door should be larger than a predetermined value in order to obtain a desired level of a sealing characteristic.
However, an excessively large value of the flexural rigidity would cause the torque for winding the film by a driving shaft to be excessively increased. Namely, due to the increased rigidity, the film door is less flexible, which makes it difficult for the film door to be neatly wound on the drive shaft. As a result, a force for winding the film door on the drive shaft is inevitably increased. Such a requirement for increasing the drive torque can be met by increasing the power which is transmitted by the drive motor. However, such an increase in the drive power necessarily increase the size of the drive motor, which is disadvantageous in view of a limited space, in the air conditioning apparatus, available for storing the drive motor. In short, there is requirements that, in order to obtain a desired sealing ability, the flexural rigidity of the film door should be larger than a predetermined value, while, from the view point of the operating force, the flexural rigidity of the film door should be smaller than a predetermined value.